In general, a foundation plate is constructed at a bottom portion of a building such that a load of the building can be uniformly distributed over the ground, upon the construction thereof, to prevent the ground from subsiding due to the building weight. In such a case, the conventional foundation plate has been designed to be constructed of thick reinforced concrete.
As the dimension of building has been recently increased, a load applied to a foundation plate is also being increased. In case of a conventional foundation plate, bending strength and shear strength have been increased in such a manner that the foundation plate constructed of general reinforced concrete is increased in size as a load to be applied to the foundation plate is increased.
As the size of the foundation plate is increased, therefore, an excavation depth should be increased enough to bury the foundation plate in the ground. Accordingly, there is a problem in that the construction period and expense are excessively consumed since the excavation work for burying the foundation plate and the manufacture work for manufacturing the foundation plate are increased in scale. In particular, in a case where a building should be constructed on a rock, the excavation work is very difficult. Thus, the construction period and expense are remarkably increased.
Further, in a case where the foundation plate is conventionally constructed of reinforced concrete, it is inevitably brought into contact with underground water as the excavation depth is increased. In such a case, if the foundation plate is in contact with underground water for a long time, there is another problem in that the reinforced concrete is deteriorated, whereby a load of building cannot be stably supported.
Furthermore, in a case where the excavation should be made deep, a desired land should be dug wider in an upward direction to prevent wall surfaces of the dug portion from collapsing and to secure as working space. If the excavation is made in such a way, it causes damage to neighboring buildings. Thus, there is a further problem in that the construction cannot be easily made at a place where the buildings stand close together. Moreover, if the excavation is made in such a manner that the desired land should be dug wider in an upward direction, a space where the concrete should be poured is increased. Therefore, there is a still further problem in that the concrete is wasted.